Optical imaging system

This application is a Continuation Application of U.S. patent application Ser. No. 18/080,333, filed on Dec. 13, 2022, which is a Continuation Application of U.S. patent application Ser. No. 16/848,152, filed on Apr. 14, 2020, now U.S. Pat. No. 11,550,126 issued on Jan. 10, 2023, which is a Continuation Application of U.S. patent application Ser. No. 16/502,485, now U.S. Pat. No. 10,656,394, filed on Jul. 3, 2019, which is a continuation of U.S. patent application Ser. No. 15/887,253, now U.S. Pat. No. 10,386,612, filed on Feb. 2, 2018, which is a divisional of U.S. patent application Ser. No. 15/187,918 filed on Jun. 21, 2016, now U.S. Pat. No. 9,952,409, which claims the benefit under 35 USC § 119 (a) of Korean Patent Application No. 10-2015-0145260 filed on Oct. 19, 2015, in the Korean Intellectual Property Office, the entire disclosures of each of which are incorporated herein by reference for all purposes.

The following description relates to an optical imaging system including lenses.

A plurality of optical imaging systems may be mounted in a portable terminal. For example, optical imaging systems may be mounted on each of a front surface and a rear surface of the portable terminal.

The optical imaging system mounted on the rear surface of the portable terminal may be used to image a subject located at a relatively long distance. On the other hand, the optical imaging system mounted on the front surface of the portable terminal is used to image a subject located at a relatively short distance. However, the optical imaging system mounted on the front surface of the portable terminal may generate an optical distortion phenomenon, such as “cone-head.” Therefore, there is a need to develop an optical imaging system capable of reducing optical distortions, such as “cone-head” distortions, and being appropriate for imaging a subject at a relatively short distance.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In accordance with an embodiment, there is provided an optical imaging system, including: a first lens including a negative refractive power and a concave object-side surface; a second lens including a concave object-side surface; a third lens; a fourth lens including a negative refractive power; a fifth lens; and a sixth lens including an inflection point formed on an image-side surface thereof, wherein the first to sixth lenses are sequentially disposed from an object side toward an imaging plane.

The second lens may include a positive refractive power.

The third lens may include a positive refractive power.

The fifth lens may include a positive refractive power.

The sixth lens may include a negative refractive power.

−35.0<{(1/f)*(Y/tan θ)−1}*100<−5.0, in which f may be an overall focal length of the optical imaging system, Y may be ½ of a diagonal length of the imaging plane, and 0 may be equal to half a field of view of the optical imaging system.

TL/2Y<0.95, in which TL may be a distance from the object-side surface of the first lens to the imaging plane, and 2Y may be a diagonal length of the imaging plane.

R1/f<−0.5, in which f may be an overall focal length of the optical imaging system, and R1 may be a radius of curvature of the object-side surface of the first lens.

−5.5<(R1+R2)/(R1−R2)<0.5, in which R1 may be a radius of curvature of the object-side surface of the first lens, and R2 may be a radius of curvature of an image-side surface of the first lens.

−1.5<f/f1<−0.05, in which f may be an overall focal length of the optical imaging system, and f1 may be a focal length of the first lens.

0.5<f/f3<2.0, in which f may be an overall focal length of the optical imaging system, and f3 may be a focal length of the third lens.

0.7<|f/f6|<1.8, in which f may be an overall focal length of the optical imaging system, and f6 may be a focal length of the sixth lens.

1.5<f/EPD<2.1, in which f may be an overall focal length of the optical imaging system, and EPD may be an entrance pupil diameter of the optical imaging system.

0.4<(t1+t2)/t3<1.3, in which t1 may be a thickness at an optical axis center of the first lens, t2 may be a thickness at an optical axis center of the second lens, and t3 may be a thickness at an optical axis center of the third lens.

0<|n1−n2|<0.25, in which n1 may be a refractive index of the first lens, and n2 may be a refractive index of the second lens.

In accordance with an embodiment, there is provided an optical imaging system, including: a first lens including a concave object-side surface; a second lens including a convex image-side surface; a third lens having including a convex object-side surface and a convex image-side surface; a fourth lens; a fifth lens; and a sixth lens including an inflection point formed on an image-side surface thereof, wherein the first to sixth lenses are sequentially disposed from an object side toward an imaging plane.

In accordance with another embodiment, there is provided an optical imaging system, including: a first lens including a concave image-side surface and a concave image-side surface; a second lens including a concave image-side surface and a convex image-side surface; a third lens including a convex object-side surface and a convex image-side surface; a fourth lens; a fifth lens; and a sixth lens including a concave image-side surface, wherein the first, the fourth, and the sixth lenses have a same refractive power, different than a refractive power of the third and fourth lenses.

The first, the second, the fourth, and the sixth lenses may include a negative refractive power.

The second, the third, and the fourth lenses may include a positive refractive power.

The fourth lens may include a meniscus shape and the fifth lens may include a concave object-side surface and a convex image-side surface.

Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.

Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience.

The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will be apparent to one of ordinary skill in the art. The sequences of operations described herein are merely examples, and are not limited to those set forth herein, but may be changed as will be apparent to one of ordinary skill in the art, with the exception of operations necessarily occurring in a certain order. Also, descriptions of functions and constructions that are well known to one of ordinary skill in the art may be omitted for increased clarity and conciseness.

The features described herein may be embodied in different forms, and are not to be construed as being limited to the examples described herein. Rather, the examples described herein have been provided so that this disclosure will be thorough and complete, and will convey the full scope of the disclosure to one of ordinary skill in the art.

Throughout the specification, it will be understood that when an element, such as a layer, region or wafer (substrate), is referred to as being “on,” “connected to,” or “coupled to” another element, it can be directly “on,” “connected to,” or “coupled to” the other element or other elements intervening therebetween may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element, there may be no elements or layers intervening therebetween. Like numerals refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be apparent that though the terms first, second, third, etc. may be used herein to describe various members, components, regions, layers and/or sections, these members, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one member, component, region, layer or section from another region, layer or section. Thus, a first member, component, region, layer or section discussed below could be termed a second member, component, region, layer or section without departing from the teachings of the embodiments.

Spatially relative terms, such as “above,” “upper,” “below,” and “lower” and the like, may be used herein for ease of description to describe one element's relationship to another element(s) as shown in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “above,” or “upper” other elements would then be oriented “below,” or “lower” the other elements or features. Thus, the term “above” can encompass both the above and below orientations depending on a particular direction of the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly.

The terminology used herein is for describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, members, elements, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, elements, and/or groups thereof.

Hereinafter, various embodiments will be described with reference to schematic views illustrating embodiments. In the drawings, for example, due to manufacturing techniques and/or tolerances, modifications of the shape shown may be estimated. Thus, embodiments should not be construed as being limited to the particular shapes of regions shown herein, for example, to include a change in shape results in manufacturing. The following embodiments may also be constituted by one or a combination thereof.

The various embodiments described below may have a variety of configurations and propose only a required configuration herein, but are not limited thereto.

In addition, a surface of each lens closest to an object is referred to as a first surface or an object-side surface, and a surface of each lens closest to an imaging surface is referred to as a second surface or an image-side surface. A person skilled in the relevant art will appreciate that other units of measurement may be used. Further, in the present specification, all radii of curvature, thicknesses, OALs (optical axis distances from the first surface of the first lens to the image sensor (OALs), a distance on the optical axis between the stop and the image sensor (SLs), a through-the-lens (TTL), image heights or ½ of a diagonal length of the imaging plane (IMGHs) (image heights), and black focus lengths (BFLs) (back focus lengths) of the lenses, an overall focal length of an optical system, and a focal length of each lens are indicated in millimeters (mm). Further, thicknesses of lenses, gaps between the lenses, OALs, and SLs are distances measured based on an optical axis of the lenses.

Further, in a description for shapes of the lenses, surface of a lens being convex means that an optical axis portion of a corresponding surface is convex, and a surface of a lens being concave means that an optical axis portion of a corresponding surface is concave. Therefore, even in the case that one surface of a lens is described as being convex, an edge portion of the lens may be concave. Likewise, even in the case that one surface of a lens is described as being concave, an edge portion of the lens may be convex. In other words, a paraxial region of a lens may be convex, while the remaining portion of the lens outside the paraxial region is either convex, concave, or flat. Further, a paraxial region of a lens may be concave, while the remaining portion of the lens outside the paraxial region is either convex, concave, or flat.

In the optical system, according to embodiments, the first to fifth lenses are formed of materials including glass, plastic or other similar types of polycarbonate materials. In another embodiment, at least one of the first through fifth lenses is formed of a material different from the materials forming the other first through fifth lenses.

An optical imaging system includes an optical system including lenses. For example, the optical system of the optical imaging system may include five lenses having refractive power. However, the optical imaging system is not limited to including only the lenses having the refractive power. For example, the optical imaging system may include a stop to control an amount of light. In addition, the optical imaging system may further include an infrared cut-off filter filtering infrared light. Further, the optical imaging system may further include an image sensor, such as an imaging device, configured to convert an image of a subject incident thereto through the optical system into electrical signals. Further, the optical imaging system may further include a gap maintaining member adjusting a gap between lenses.

First to sixth lenses are formed of materials having a refractive index different from that of air. For example, the first to sixth lenses are formed of plastic or glass. At least one of the first to sixth lenses has an aspherical shape. As one example, only the sixth lens of the first to sixth lenses may have the aspherical shape. In addition, at least one surface of all of the first to sixth lenses is aspherical. In an example, the aspherical surface of each lens may be represented by the following Equation 1:

In this equation, c is an inverse of a radius of curvature of the lens, k is a conic constant, r is a distance from a certain point on an aspherical surface of the lens to an optical axis, A to J are aspherical constants, and Z (or SAG) is a distance between a certain point on the aspherical surface of the lens at the distance Y and a tangential plane meeting the apex of the aspherical surface of the lens.

In accordance with an embodiment, an optical imaging system includes six lenses, a filter, an image sensor, and a stop. Next, the above-mentioned components will be described.

The first lens has a refractive power. For example, the first lens has a negative refractive power.

At least one surface of the first lens is concave. For example, an object-side surface of the first lens is concave. In one example, an image-side surface of the first lens is concave in a paraxial region and gradually outwardly curves (such as inflection points), at edge portions thereof. An object-side surface of the first lens is concave in the paraxial region and gradually flattens at edge or end portions of the first lens.

The first lens has an aspherical surface. For example, both surfaces of the first lens are aspherical. The first lens is formed of a material having high light transmissivity and excellent workability. For example, the first lens is formed of plastic. However, a material of the first lens is not limited to plastic. For example, the first lens may be formed of glass.

The second lens has a refractive power. For example, the second lens has a positive refractive power or a negative refractive power.

At least one surface of the second lens is convex. For example, an image-side surface of the second lens is convex. In this example, an object-side surface of the second lens is concave in a paraxial region. In another embodiment, an image-side surface of the second lens is concave and the object-side surface of the second lens is convex. In one embodiment, end portions of the object-side surface of the second lens overlaps, at least in part, with at least a portion of the first lens. In another embodiment, the second lens is spaced apart from the first lens.

The second lens has an aspherical surface. For example, an object-side surface of the second lens is aspherical. The second lens is formed of a material having high light transmissivity and excellent workability. For example, the second lens is formed of plastic. However, a material of the second lens is not limited to the plastic. For example, the second lens is formed of glass.

The third lens has a refractive power. For example, the third lens has a positive refractive power.